Thin-layer chromatography in testing the purity of pharmaceuticals

For a considerable time, thin-layer chromatography (TLC), or planar chromatography (PC), was called the “Cinderella” or the “Princess” of chromatographic techniques. This expression was chosen to characterize the ability of this versatile method to be renewed and “reinvented” over and over again. Unfortunately, today, only classical, semi-quantitative TLC procedures can be found in the various (and conservative) pharmacopoeias. In addition, the number of TLC applications is steadily decreasing, being replaced by HPLC methods that are considered more appropriate. The newest developments in instrumental TLC are more or less neglected by the pharmacopoeias, but can nevertheless be used by analysts in both research and quality control as it is a fast, relatively low-cost technique. This article surveys recent developments in instrumentation of TLC and some examples of applications from different fields of pharmaceutical analysis, and expresses hope for the future of this method.